Will the Southland wind up holding much of the $17-billion bill for the delta water tunnels?

Some of the state’s biggest water districts are about to make their opening moves in a financial chess game that ultimately could saddle the Southland with much of the bill for re-engineering the failing heart of California’s water system.

In coming weeks, the districts are expected to decide if they want to sign on to California WaterFix — a long-planned proposal to construct two massive tunnels that would change the way water supplies move through the Sacramento-San Joaquin Delta.

Backers long have operated under the assumption that the cost, now estimated at nearly $17 billion, would be split among customers of the big government water projects according to the size of their contracts for delta supplies.

Under that scenario, the largely urban agencies supplied by the State Water Project would pick up 55% of the tunnel tab, and the largely agricultural districts supplied by the federal Central Valley Project would pay for 45%.